The present invention relates to vehicle suspension systems and more particularly to vehicle suspension system in which a plurality of wheel and hub assemblies are each connected to the body of a vehicle by one of a plurality of actuators and the operation of each actuator is controlled by an electronic or electrical processor.
Suspension systems according to the invention have been described as "active" suspension systems, Such suspension systems are well known and have been described in patent applications such as European patent publication Nos. 0114757 and 0190944.
It is a problem with an active suspension system to control the suspension system upon failure of one of the sensors. Obviously, it is very undesirable for the suspension system to fail completely on failure of a sensor. This can be highly dangerous in a situation where the vehicle is manoeuvering at high speed and can lead to accidents.
In fly-by-wire systems in aircraft generally several identical control systems are run in parallel and the output of each control system is checked against the output of the others. If one control system has a different output from the others then it is assumed to be faulty and therefore shut down. The costs of such an approach and the limited space in a motor vehicle make the approach impractical for controlling a land vehicle suspension system.